div.topbox {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 60px;
}

div.contentbox {
    height: calc(100% - 100px);
    overflow: auto;
}

div.pagebox {
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
}